Steve McCormick reports that using his amps with the ZEROs to drive 4 ohm speakers sounds better than driving the speaker directly, despite the fact that his amplifiers are easily capable of driving 4 ohms.
I interviewed several solid state amplifier manufacturers at CES this year, all of which made amps that are considered 'high current' and easily double power into 4 ohms. There was a consensus amongst them; transistor amplifiers will sound better into 16 ohms than they will into 4, apparently due to the effects of current through the output devices, which is deleterious to the sonic performance **even though the amp easily makes the power**.
This is a powerful argument for using the ZEROs with any transistor amplifier as this precisely what it does: loads the amp at 16 ohms.
You will loose power this way with a transistor amp- a 100 watt amplifier will suddenly be putting out 50 watts, but it will be a better-sounding 50 watts.
The effect of using tubes with the ZERO is different- in many cases you do get better sound, but in some cases you also get more power and wider bandwidth, especially in the bass. Most transformer-coupled tube amps suffer a loss of power and low frequency bandwidth when running on the 4 ohm taps; the ZERO is a way around this.
